Effects of Consuming Protein Shakes, Varying in Protein Source, on Appetite, Satiety and Energy Intake

Background: Consistent data from acute, single preload studies demonstrate improvements in perceived appetite and satiety following the consumption of high-protein preloads compared to normal protein preloads. However, it is currently unclear as to whether protein quality (i.e., protein source) or the use of appetite questionnaires influences these outcomes. Objective: To examine whether the consumption of protein preloads (egg white isolate, whey isolate, micellar casein, and instant egg white) differentially modulate postprandial hunger, fullness, desire to eat, prospective food consumption, eating initiation, and subsequent food intake; and if the use of appetite questionnaires to assess perceived appetite and satiety affect subsequent energy intake. Methods: Twelve young adults (age: 22±1 y; BMI: 22.1±0.9 kg/m2) reported to the research facility between 7 - 9 am to complete each 4-h testing day. A set of questionnaires assessing perceived hunger, fullness, desire to eat, prospective food consumption were completed followed by the consumption of the 130 kcal beverage preloads, varying in protein source. A water preload was also included as a control. The same set of questionnaires along with the assessment of whether they would like to eat again were completed every 30 min throughout the 4-h postprandial period. On a separate day, all twelve young adults also completed a similar testing day except were not given questionnaires throughout the 4-h postprandial period. After the 4-h, the participants were given an ad libitum pasta meal to consume until 'comfortably full.' Results: The consumption of the protein preloads improved hunger, fullness, desire to eat, prospective food consumption and delayed the request to eat again vs. the control (water); however, no differences in appetite and satiety outcomes were observed between protein sources. No differences in energy content at the lunch meal were observed between any preloads. The use of questionnaires did not ch